Anisotropy in the magnetization and resistivity of the metallic triangular-lattice magnet PdCrO2

Abstract

We report results of our magnetization and resistivity measurements using single crystals of the conductive antiferromagnet PdCrO2 with a layered structure, consisting of alternating stacks of a triangular lattice of Pd1+ and of Cr3+ along the c axis. We confirmed that the magnetic susceptibility is nearly isotropic above TN but becomes slightly anisotropic below TN (χab > χc). These results, combined with previously known facts, indicate that PdCrO2 is a Heisenberg spin system, and the spins lie in a plane containing the c axis below TN (an "easy-axis type" 120° structure). We also found that the resistivity exhibits a highly two-dimensional metallic behavior in the whole measured temperature range with an anisotropy ratio ρc/ρab ≥ 150. Interestingly, despite such a strongly anisotropic conductivity, the inter-Pd-layer hopping and the intra-Pd-layer conductivity are both affected by the localized Cr spins in comparable magnitude. The present results make PdCrO2 a promising candidate for the emergence of the unconventional anomalous Hall effect.